Oh so now since you've lost the electrical conductivity argument, you're switching to thermal conductivity. Nice work. That's kinda like changing global warming to climate change, ain't it?
I haven't found the first thing that backs up any of that. In fact, all I can find is copper has the least resistance. Period. I'm all about learning and I'm the first one that'll admit I'm wrong, but so far I see no proof of it, but quite the opposite.
Resistance doesn't matter that much. We put 4k ohm resistors into spark plugs to kill RFI noise (and wires too, most have a pretty high resistance!).
*edit*
Turns out, the resistance also helps kill capacitive after-fire (a second spark after the initial spark, caused by the capacitance of the leads and spark plug body). Capacitive after-fire won't help an engine run better, but can wear electrodes faster. The resistance of plug wires and spark plugs also helps limit current through the ignition system to prevent burning out coils and distributors. Low-resistance wires are often marketed with hype about their low resistance, but in reality they simply add a highly conductive material that makes them 'measure' low, but in reality are not a significant part of the electrical path for the spark and therefore don't actually improve anything. But a lighter wallet does go faster, right?
*end of edit*
Low resistance won't do anything either since spark plugs and wires work on inductance not conductance. I'm not an EE, but I do know for a fact that resistance doesn't matter much if at all (until it's so high as to create an open circuit). High voltages overcome resistance quite easily, however it does it.
I'm trying to find the charts and graphs which show the change in breakdown voltage for spark plugs based on standard vs iridium, vs platinum. I know I've had several motorcycles which require iridium plugs because the charging system was too weak to keep copper plugs clean!
Here's at least one source, with quotes from Autolite's director of engineering, stating that the fine wire iridium plugs can reduce coil requirements by as much as 20% - which means by switching to iridium, one could open the spark gap considerably with a stock coil.
Also notable:
"Fine-wire iridium plugs can improve the combustion process even if there is a high level of exhaust gas dilution—built-in EGR—as with engines with long-duration camshafts with a greater amount of overlap."
448Scamp.
I knew I had seen advertisements for NGK Copper splugs from my motorcycling days.
Went through some old magazines & this ad was on page 11 of Cycle Guide magazine, July 1969. 'Exclusive Hear-of-Copper guarantees the widest heat range. Cuts tip erosion & fouling...'
The Jerry Reeves link says towards the end. 'Lets look at some facts that support fine wire plugs are a good choice for a performance engine..'
Resistance doesn't matter that much. We put 4k ohm resistors into spark plugs to kill RFI noise (and wires too, most have a pretty high resistance!).
*edit*
Turns out, the resistance also helps kill capacitive after-fire (a second spark after the initial spark, caused by the capacitance of the leads and spark plug body). Capacitive after-fire won't help an engine run better, but can wear electrodes faster. The resistance of plug wires and spark plugs also helps limit current through the ignition system to prevent burning out coils and distributors. Low-resistance wires are often marketed with hype about their low resistance, but in reality they simply add a highly conductive material that makes them 'measure' low, but in reality are not a significant part of the electrical path for the spark and therefore don't actually improve anything. But a lighter wallet does go faster, right?
*end of edit*
Low resistance won't do anything either since spark plugs and wires work on inductance not conductance. I'm not an EE, but I do know for a fact that resistance doesn't matter much if at all (until it's so high as to create an open circuit). High voltages overcome resistance quite easily, however it does it.
I'm trying to find the charts and graphs which show the change in breakdown voltage for spark plugs based on standard vs iridium, vs platinum. I know I've had several motorcycles which require iridium plugs because the charging system was too weak to keep copper plugs clean!
Here's at least one source, with quotes from Autolite's director of engineering, stating that the fine wire iridium plugs can reduce coil requirements by as much as 20% - which means by switching to iridium, one could open the spark gap considerably with a stock coil.
Also notable:
"Fine-wire iridium plugs can improve the combustion process even if there is a high level of exhaust gas dilution—built-in EGR—as with engines with long-duration camshafts with a greater amount of overlap."
Yes sir, I read that. And the only thing I read that was performance oriented was that a fine wire plug takes less voltage to ionize the gap. I don’t think anyone here would argue that. I don’t think anyone here would argue that a precious metal center electrode will last longer than a copper electrode plug. I do know that several ignition engineers I’ve spoken with all have a different opinion of how the ionization of the gap occurs. And that’s an issue because depending on which understanding you follow will directly impact the choice of spark plug. Also in the conversation must be the fact that current OE ignition systems are miles ahead of what most here on a forum like this use. These OE ignitions will fire less than optimal chamber conditions (either rich or lean of stoich and even at that it’s only stoich to about 5% rich for best chamber conditions near the plug) much better than say the Chrysler ignition or the many knockoffs of that concept or even the much ballyhooed HEI. In the case of running these less efficient and powerful ignition systems, a precious metal center electrode can cause an undetectable misfire, which in turn causes an O2 sensor to read rich when the engine isn’t really rich at all. In the end when all the chatter has fallen away, it remains if the ignition is up to snuff then the only benefit to a precious metal center wire is its working life span.
Which is exactly why these plugs were developed. Because the ignition system was so weak you get misfires. The benefit of longer life was a byproduct of that plug development. The correct answer is get the best ignition system you can find. And use a precious metal electrode plug if you don’t want to change your plugs very often and you don’t mind a lighter wallet. And at that none of this addresses the issue of a copper electrode plug causing ionization to occur easier than other electrode types. Even the engineers can’t agree on that.
Note entirely. Both platinum and iridium deal with heat better. As a result, they can be run 'hotter' without as much concern for preignition. That means the plugs stay cleaner, and they also stay sharper longer - which means better spark for longer, or better spark with a 'hotter' ignition system longer than a copper plug would last. It also means that they deal with non-ideal conditions better since the plugs are better able to fire with increased EGR, sub-optimal AFR, and will put up with abuse for much longer than copper.
My take is this: tune with copper, fine-tune with platinum or iridium after and then enjoy the car. There's no reason to run a tuned-up engine with anything but platinum or iridium, especially with a souped up ignition (MSD, etc). IMO: copper doesn't last, doesn't stay in-tune (no one replaces plugs before fiddling with the carb), and aren't well suited to anything but stock applications. As soon as you have more spark, more cam, more abuse, copper just stops making sense.
I wouldn’t argue any of that. My thinking is plugs are cheap. I still am not sold that other than the fact that the center electrode is a fine wire that the fine wire plug does any better at firing than a copper electrode. Even in the link Bewy posted the author never really developed any thoughts that I haven’t heard before, and that is the life span of these plugs is better. I’m still in the camp that if you can get to your plugs the copper electrode is better. I think that some wear of the center and ground electrodes makes firing the gap much easier and more consistent up to the point they increase the gap so far the ignition can’t keep up. I think this is a case of the technology adapted by the OEM’s doesn’t always translate to what people on a forum like this do. I also appreciate your comments on plug wires. I’ve spent a lot of money on plug wires with very low resistance and they were not half as good as some plug wires that had more resistance. It’s marketing hype for sure.
Which may or may not be the right heat range. A guy in another thread is tearing his hair out with a rich running condition and I bet it's related to too cold of a heat range.Kent, they probably recommend those plugs mostly I bet because they are the small 5/8 hex and easier to get to. I'm sure they are "whatever" heat range Trick Flow thinks is best.